Expansion pilot



W. H. EVANS Sept. 8, 1931.

YLL ITANS ION PILOT "W 5 OWL. 18, 1929 Patented Sept. 8, 1931 UNITEDSTATES PATENT OFFICE WILLIAM H. EVANS, OI CHIQAGO, ILLINOIS EXPANSIONPILOT Application filed October 18, 1829. Serial No. 400,598.

My invention relates in general to expansion pilots, and more inparticular to a pilot adapted to serve as a guide for a reamer used oninternal combustion engines.

en a valve seat is dressed up with a reaming tool, it is of primeimportance that the axis of the reamer be held positively and directlyin line with the center line of the valve and stem. When the valve is inplace on a motor, the stem, of course, extends into the valve stem guideand the valve, as a whole, reci rocates therein. Pilots for reamers arema e to utilize the valve stem guide for centering purposes. Many typesof pilots have a guide shank formed integral therein and are adapted toproject into the valve stem guide to center the pilot and the reamercarried by the pilot. The diameter of valve stem guides variesconsiderably, however,

and it has been the vogue recently to employ a separate pilot guide withthe contact points where they engage the inside walls of the valve stemgu1de adjustable, whereby the same pilot guide may be employed forseveral different stem guide diameters. The pilot head has an internalcentral bore of standard diameter corresponding with the standarddiameter used in the top of the pilot guide, which is adapted to entersaid central bore.

In this way only a single pilot head is required, and a smaller numberof pilot guides, than would otherwise be necessary, due to theadjustable feature thereof.

I have found that the pilot guides heretofore employed have not beencapable of adjustment over a sufliciently large diameter. Some of thebest of them. I have found, can be adjusted only over a range of aboutten thousandths of an inch. While such guides are an improvement in somerespects over the old style pilot having an integral guide shank, theyare deficient in several respects. I wish to make it clear that anypilot guide shell can be made to expand over for instance, but it cannotbe held from turning over such a range, and consequently, in actual use,can be expanded only approximately a few thousandths of an inch. This isthe case when the guide is operated solely from the top of the valvestem guide, but when and if the shell can be held at the bottom, arelativelyblwide range of adjustments is easily poss1 e.

Accordingly, one of the principal objects of my invention is theprovision of an improved reamer pilot.

Another object is the provision of an improved reamer pilot ide.

Another object is t e rovision of a reamer pilot guide capable ofadjustment over a so much wider range of diameters.

Other objects and features of the invention will be apparent from aconsideration of the following detailed description, taken with theaccompanying drawings, wherein- Fig. 1 is a perspective view of theimproved pilot guide;

Fig. 2 shows the pilot guide in use for centering a reamer duringoperation on a valve seat;

Fig. 3 is an enlarged fragmentary sectional view showing some of thefeatures of the guide;

Fig. 4 is a sectional view taken on the line 4-4 of Fig. 3; 7 Fig. 5 isa perspective view of a modified form.

Referring now to the drawings, the pilot guide includes a shell 10, ofgeneral tubular shape, having a closed end 11 and interior threads 12into which a guide shank 13 is adapted to be threaded. The shell 10 isprovided with a number of end slots 14, so positioned that when theshank is screwedinto the shell, the resulting tines or prongs 16 on theshell are adapted to ride up over a cam surface 17 on the shank, formedby the sharply increasing diameter of the shank at this point. The shell10 is made of a high grade spring steel and the tines 16, therefore, canbe expanded outwardly a considerable distance, or forced inwardlywithout strain on the material thereof.

In order further to understand the construction and operation of theshell 10, the

'pilot and details thereof will now be referred to. The guide shank 13has three sections 18, 19, and 21, each of substantially constantdiameter of some lineal range, but the diameter between each oneincreasing slightly. The

portion 18 is relatively narrow and is adapted to be wholly enclosed bythe shell 10. The

cam portion 17 connects'the sections 18 and 19, the section 19 beingnarrow enough to clear the walls of the valve stem guide under allcircumstances without binding. Between portions 19 and 21, there is atapered portion 22, and the portion 21 is larger than the largestdiameter valve stem guide on which this particular pilot will be used.The tapered portion 22 is adapted to be wedged down into the top of thevalve stem guide, so that with the tines 16 of the centering shellexpanded and the tapered portion 22 wedged down into the top of thevalve stem guide, the pilot guide as a whole will be positively centeredwith respect to the valve stem guide because it will be supported atthree points.

Looking at Fig. 2, a small section of a motor block is shown with avalve stem guide 23 and the pilot guide positioned therein. A pilot head24 is shown provided with a central bore 26, into which the portion 21of the pilot guide extends. A tapered portion of the head is adapted toreceive a reamer 28 supported thereon frictionally, as is customary inthe art. Above the tapered portion 27, threads 29 are provided on whicha nut 31 is threaded, this nut being employed for the purpose of forcingthe reamer 28 ofi its tapered support.

The reamer is shown in position to dress up a valve seat 32. The pilothead has a transverse opening 33 for receiving a suitable tool forturning the same, and also has a square upper end 34, also adapted foruse with a suitable tool to turn the reamer. The pilot guide is alsoprovided with suitable tool engaging means for the purpose of turning itwithin the valve stem guide, a transverse opening 36 being shown.

I shall now refer more fully to the con-- struction of the pilot guideshell and its tines 16. The shell is designed so that, under allcircumstances. within the range of adjustment for which the pilot isadapted, the friction between the inside of the shell and the shank 13will be less than the friction between the outside of the shell and theinside surface of the valve stem guide. This is brought about by theutilization of certain details of construction which may be modified,within certain limits.

As the drawings show, the tines are provided with relatively sharppoints 167) and have flat places 16a resulting in the formation oflongitudinal ridges or relatively raised portions, two in number, foreach tine. The result of this construction is that the cam portion 17engages the points of the tines, while at the outside of the tines thereare two points of engagement between the tines and the inner surface ofthe valve stem guide. Not only does less friction result on the in- 65side than on the outside, but in this construction the friction isdouble on the outside of what it is on the inside. With three tines asshown, there are three points of engagement on the inside of the shellwith the cam surface 13, while there are six oints of engagement betweenthe outside 0 the shell and the inside of the valve stem guide.

The design of the shell will be still further understood by aconsideration of the manner in which it is produced, it beingunderstood, of course, that I am not limited by any particular method ofmanufacture.

The shell is first produced unslotted, the outside diameter thereofbeing the mean between the maximum and minimum adjustment to which theshell will be subjected. For example, if a one thirty-second adjustmentwill be required above and below threecighths of an inch, the size ofthe shell itself would be made exactly three-eighths of an inch, so thata one sixty-fourth adjustment would take place each way. The shell isthen subjected to a forming operation to produce six equally spaced flatportions such as shown at 16a, and is then slotted or kerfed by means ofa saw or other suitable tool, with the slots extending through alternateflat portions, leaving the remaining flat portions equally spacedbetween the slots. This produces a somewhat flat construction in theneighborhood of the slots, as the slot does not quite occupy the entirewidth of the flat portion. The tines are then shaped to a point, usuallyby making a pair of side angular cuts into the main cuts, and the insideis then reamed to 100 form a flat taper on the under side of the tineends as shown. The radius of curvature of the outside of the shell isless than the inside of the valve stem guide, as a rule, but independentof the relative radii of curvature, the two engaging portions on theoutside of the shell will compensate for any difference in diameter andwill always engage independent of the diameter. The radius of curvatureof the under side of the 10 tines is less than the curvature of theshank, so that independent of the engagement of the points on the tines,there is no possibility of the entire area of the inside of the tinesbearing upon the shank so as to increase'the friction therebetween.

As previously stated, the specific construction of the shell can bemodified. Instead of three tines 16. a'larger number can be employed andthe flat place 16 can be made concave or any shape to relieve the metalat this point, and offer increased friction to the turning of the shellin the guide. This fiat portion can be cut clear through, if desired,forming a number of smaller tines, as in the modified View, Fig. 5,shows. The point 116!) or each one of the smaller tines is brought downto limit the engagement with the cam surface 17 in the manner shown. Thecorresponding parts of the shell are indicated 136 by the same numeralsas employed in the main figures, but with the prefix 1 added.

Another advantageous feature of the invention, which I wish to pointout, is that the shell 10 is closed at its lower end. This positivelyprotects the inside of the shell, the screw threads, and other parts ofthe device, from contamination and injury by carbon or other matterwhich may be encountered in the valve stem guide. This arrangement alsoprevents the injury of the threads during the time the tool is handledabout a shop.

The operation of. the tool appears clear from the description thereof,but, in-general, I wish to say that in inserting the tool into the valvestem guide, it is customary to turn the shell partly off the shank, sothat the cam surface 17 is entirely clear of the tines. This permits thetines to be forced inwardly pilot guide including a guide shank having acam surface and a centering shell threaded on said shank, said shellhavin a plurality of tines provided with relative y pointed ends, andlongitudinally disposed fia-tsections forming side ridges, the ridges atthe sides of the flat sections engaging the inside surface of a valvestem guide to prevent turning of the shell independent of the diameterof the ide within the limits for which the pilot is designed, and saidpointed ends engaging said shank at only a single point on the camindependent of the relative adjustment. v In witness whereof, I hereuntosubscribe my name this 16th day of October, 1929. WILLIAM H. EVANS.

as the tool is thrust into position, and, as previously described, thespring tension of the tines themselves is suflicient to hold the shellin place as the shank is drawn up tightly.

The advantage of my tool over those of the prior art may be apparentwhen it is stated that one guide of this character is sufiicient for alarge number of valve stem guides, and I have found that practicallyevery make of automobile can be fitted with a set of three guides ofthis character. I know of no pilot guide heretofore in use which can be'made to operate on all t pes of automobiles, unless at least eleven dierent guides were furnished.

I have described my invention somewhat in 7 detail in order that thoseskilled in the art will understand the same fully, but I do not restrictmyself to the details shown and described, the invention being limitedonly by the scope of the claims.

What I claim as new and, desire to protect by Letters Patent of theUnited States is:

1. In a pilot for a valve seat reamer, a pilot guide including a shellwith end slots to form a plurality of tines and a shank threaded intothe shell with a cam surface for engaging the tines at a single point toexpand them inside a valve stem guide, the tines having single camengaging points at the ends and having a central longitudinal area belowthe normal curved surface thereof, whereby a greater frictionalengagement exists on the outside of the shell than on the inside.

2. In a pilot for a valve seat reamer, a pilot guide including a guideshank having a. cam surface and a centering shell threaded thereon, saidshell being slotted to form a plurality of tines, said tines havingoutside longitudinal ridges to offer relatively great friction toturning of the shell within a valve seat guide, but permitting freebodily longitudinal movement of the shell along said valve stem guidethe tines having a single point of engagement on the cam surface and aplurality of points engagement with the valve seat guide.

Ii. In a pilot for a valve seat reamer, a

